The present invention relates to a novel wet deck fill preferably made from a light weight thermoformed plastic material. The wet deck fill includes a plurality of adjacent wet deck fill sheets made in accordance with the present invention.
The wet deck fill is used as heat transfer media in evaporative type counterflow heat exchanger apparatus, such as cooling towers, which are used primarily to cool water for such applications as air conditioning, food processing and numerous other industrial processes.
One example of a general prior art wet deck fill arrangement disclosing how it is used in evaporative heat exchange apparatus is illustrated and described in U.S. Pat. No. 3,442,494, issued May 6, 1969 to Engalitcheff, Jr., et al., including the present inventor. The wet deck fill sheets in this patent are made of sheet metal and are fairly typical of prior art wet deck fill. In more recent years, wet deck fill has been made of thermoplastic polymeric resins having horizontal corrugations, but they have not had the structural integrity and are not of a suitable design to most efficiently be manufactured and used to provide optimal thermal performance to achieve a maximum air-water contact area and dwell time, while maintaining low air pressure drop characteristics.
The state of the prior art can best be described by reference to the following U.S. patents.
Pat. No. 2,793,017 issued May 21, 1957 to Lake is believed to be the closest prior art known to the inventor. This patent discloses wet deck fill comprising sheets having longitudinal corrugations and short, transverse corrugations extending from the top and bottom edges of the sheet to the top and bottom longitudinal corrugations, respectively. In addition, vertical spacing ribs are disposed in a staggered arrangement and extend from the front face of the sheet. When the sheets are assembled to form a wet deck fill section, the transverse edge corrugations of one sheet contact the transverse edge corrugations of the adjacent sheets to form a honeycomb arrangement at the top and bottom of the fill section. This arrangement adversely affects the water distribution on the surfaces of the sheets. Further, this arrangement increases the air pressure drop compared both to the present invention and to prior art fill sheets having uncorrugated top and bottom edges.
The following U.S. patents disclose various types of spacing means associated with wet deck fill sheets to keep the sheets separated by a predetermined distance.
Pat. No. 2,596,642, issued May 13, 1952 to Roestad, discloses sheets having corrugated edges. A plurality of stiffening spacers called ridges are formed in the sheets. The spacer ridges are vertically aligned or extend almost the full height of the sheets.
Pat. No. 3,132,190, issued May 5, 1964 to Engalitcheff, Jr., discloses the use of spacer strips which hang from the top of wet deck fill sheets. The longitudinal corrugations of the fill sheets bear against the spacer strips and are thereby separated from each other.
Pat. Nos. 3,540,702, issued Nov. 17, 1970 to Uyama, 3,733,063, issued May 15, 1973 to Loetel, et al., 3,963,810, issued June 15, 1976 to Holmberg, et al., and 3,994,999, issued Nov. 30, 1976 to Phelps, all disclose spacing means including substantially circular projections extending from the front face of the wet deck fill sheets. The spacer elements bear against certain portions of the rear face of adjacent sheets to maintain the desired distance between the sheets. The Phelps patent also discloses an embodiment of a wet deck fill in which the sheets are aligned so that the longitudinal corrugations extend vertically, rather than horizontally. In this embodiment, the sheets are spaced from each other by flat, horizontally disposed spacer elements located between the sheets at the top and bottom of the fill.
Pat. No. 3,804,389, issued Apr. 16, 1974 to Engalitcheff, Jr., et al., including the present inventor, discloses the use of several wet deck fill layers disposed one above the other. Each of the layers is very short in height and includes a single concavo-convex curved portion between upper and lower marginal portions, and has a total height of about 4-1/4 to 4-1/2 inches. Extending from the concave side of the sheet, including the margin areas, are several spacing tabs. The tabs bear against the convex surface, again including the margins, to space the fill sheets from each other.
Pat. No. 3,965,225, issued June 22, 1976 to Schinner, discloses a wet deck fill comprising aligned, corrugated fill sheets which include a number of spacer-turbulators consisting of a series of mounds having a peak and crest at each corrugation. The spacer-turbulators extend substantially the full height of each of the sheets. The top of the crests bear against the concave portion of the adjacent fill sheet to keep the fill sheets spaced apart.
The following U.S. patents relate to modifications made to wet deck fill sheets in an effort to improve water distribution on both the front and rear faces of the sheets. Pat. No. 2,042,127, issued May 26, 1936 to Sayles, discloses a wet deck fill comprising fill sheets having angled tongues formed on the upper edges. Alternate tongues are angled in opposite directions so that water hitting one tongue is directed to one side of the sheet and water hitting the adjacent tongue is directed to the other face of the sheet. Provisions are also made for interlocking superimposed layers of fill material with each other. The interlocking occurs by having slots formed on the bottom of one fill layer interlocked between adjacent tongues on the top of the next lower fill layer.
Pat. No. 2,783,982, issued Mar. 5, 1957 to Kahl, is similar to the Sayles patent in that clip members are provided for securing separate alternating angled tongues on the top of fill sheets.
Pat. Nos. 3,415,502, issued Dec. 10, 1968 to Munters, and 4,218,408, issued Aug. 19, 1980 to Henning, et al., disclose other embodiments of wet deck fill sheets having various types of corrugations.
None of the above-described prior art provides the advantages of the present invention. The wet deck fill using wet deck fill sheets made according to the present invention overcomes the problems of the prior art and provides a surprising result in improved air pressure drop characteristics and thermal performance, including maximizing air-water contact area and dwell time. The fill has a high structural strength without increasing the weight of the fill. Moreover, wet deck fill sheets of the present invention can be manufactured at low costs.
Other advantages of the present invention and various comparisons of the present invention with prior art wet deck fill will be set forth hereinafter.